试试这个

buttonRef.addEventListener("click", function() {
    alert("Blah blah...");
}, false);

其中"buttonRef"是对按钮的引用.

Where ''buttonRef'' is a reference to button.

var DownArrow = document.createElement("img");
DownArrow.onclick = function () { return verticlescroll('down'); };

function verticlescroll(arrowDir) {
.......code
}